Joseph Jakubowski is considered armed and highly dangerous.

A MASSIVE MANHUNT is underway in search of a “highly-dangerous” Wisconsin man who US authorities said robbed a gun shop and sent a lengthy manifesto to President Donald Trump.

Some 150 local, state and federal police officers and personnel were searching for Joseph Jakubowski, 32, who last Tuesday allegedly stole some 16 “high-end firearms” from a gun store in Janesville, Wisconsin and set fire to a car nearby, according to Rock County Sheriff Robert Spoden.

Spoden said the suspect had written a 161-page long anti-government manifesto, which he had posted to the White House. Police obtained a copy.

“Joseph Jakubowski has been highly agitated by national politics recently,” Sheriff Robert Spoden told journalists on Friday, adding that an associate said Jakubowski “recently verbalised a plan to steal guns and use them in an unspecified attack”.

Spoden described the manifesto as “a long laundry list of injustices that he believes the government and society and the upper class have put forth onto the rest of the citizens”.

He added that the suspect had acquired a bulletproof vest and a helmet and was considered “armed and highly dangerous”.

The threat prompted some schools to close on Friday.

Patrols were also increased at local churches “as a result of anti-religion sentiment depicted in Jakubowski’s manifesto,” the sheriff’s department said in a statement yesterday.

The city of Janesville, located some 100 miles northwest of Chicago, is the hometown of US House Speaker Paul Ryan.